A process monitoring and control system may include wireless sensors used to measure various characteristics within an industrial facility. Physical transducers coupled to or used in the wireless sensors may have any of several types of electrical characteristics, such as high-level analog inputs (HLAIs), low-level analog inputs (LLAIs), and digital (ON/OFF) contact-closure inputs. Example HLAI signal sources include 0-20 mA or 4-20 mA current sources. Example LLAI signal sources include thermocouples and other sensors with outputs ranging from ±0.01V to ±0.1V.
In conventional systems, it is typically necessary to add a current shunt resistor across input terminals of a wired or wireless sensor in order to change an input of the sensor from accepting a low-level (voltage) input to accepting a high-level (current) input. Adding or removing the current shunt resistor requires access to field wiring terminals in order to manually add or remove the resistor from the sensor. An alternate approach uses an electromechanical switch to break the circuit to the shunt resistor, but this approach still requires physical access to the sensor in order to operate the switch manually.
Physical access to a sensor may be difficult or dangerous. For example, the sensor may be located in a hazardous environment or a difficult-to-access location, such as at the top of a tower. Also, for protection from moisture or corrosive environments, electronic components in a sensor may be conformally coated, making it impractical to use a removable resistor or an electromechanical switch.